1. Field of the Invention
The present invention relates to a method and apparatus for treating obstructive sleep apnea by using negative oral pressure to a patient.
2. Description of the Related Art
Obstructive sleep apnea (OSA) occurs when the muscles in the back of people's throat relax in which people stop breathing sometimes hundreds of times a night for up to a minute each time. FIG. 1A depicts a normal breathing condition of people when sleeping in which the nasal breathing air passageway is kept open. FIG. 1B depicts an upper airway resistance syndrome of people when sleeping in which the dimension of the nasal breathing air passageway is narrowed due to relax of the back muscles of the throat. FIG. 1C depicts an obstructive sleep apnea occurs when sleeping in which the nasal breathing air passageway is obstructed by the collapsing muscles in the back of the throat.
More than 10% population is affected by sleep apnea but only a small fraction of patients are treated. People with sleep apnea have much higher life risks; for example having, excess mortality: there are 36% decrease in survival over 8 years in untreated patients with an apnea index of ≧20 as compared to untreated patient with an apnea index of <20, excess risk of hypertension: there is an odds ratio of 2:1 for a patient with Respiration Disorder Index (RDI)=5 as compared to a person without sleep apnea and an odds ratio of 5:1 for a patient with RDI=25 as compared to a person without sleep apnea, excess risk of myocardial infarction (MI): a patient with sleep apnea has 23-fold increased risk of recurrent MI, excess risk of stroke: an odds ratio of stroke is up to 3:2 for a patient with sleep apnea as compared to a person without sleep apnea, and risk of vehicular accidents: it is 7-fold higher for the untreated patient than a person without sleep apnea and 12-fold higher for the untreated patient if corrected for mileage.
There is no perfect resolution exists. The constant positive airway pressure (CPAP) method as shown in FIG. 2A is the most popular option, in which constant positive pressure air is supplied through a mask 20 to the patient to keep the nasal breathing air passageway open, but this option suffers a low patient compliance rate of 40˜50% due to discomfort caused by positive pressure and high air flow. Other treatments include soft tissue removal, skeletal surgery and wearing an oral device. Referring to FIG. 2B, the soft tissue removal is to remove soft tissue such as soft palate, uvula and tonsil etc., as indicated in part B, to enlarge the dimension of the nasal breathing air passageway. FIG. 2C depicts a kind of skeletal surgery called bimaxillary advancement, by which a first fastener 22 is placed in the mandibular portion to push the mandibular portion forward and a second fastener 24 is placed in the upper palate such that the upper palate can be aligned with the mandibular portion. By pushing the mandibular portion forward, the tongue is pulled forward to enlarge the dimension of the nasal breathing air passageway. A comparison of different methods for treating obstructive sleep apnea is shown in Table I.
TABLE IEfficacyfortreatingPatientCostMethodCure forOSAComplianceConvenience(US$)InsuranceOralSnore,20~40%50~60%Not much$$$CoveredDeviceMild OSACPAPSnore,75~85%20~50%Not at all$$$~$$$$CoveredMild-SevereSoft TissueSnore,<40%100%Yes$$$$Case byRemovalMild OSAcaseSkeletalModerate-40~97%100%Yes, except$$$$$Case bySurgerySevereTracheostomycaseOSA
According to Table I, some of the above methods have high patient compliance but low efficacy and also high prices, some of them have high efficacy, low prices but also low patient compliance as well as low convenience.
It is desirable to provide a method and an apparatus for treating OSA, which can alleviate the drawbacks of the above methods.